Screw extrusion additive manufacturing of thermoplastic polyolefin elastomer

Abstract This study determined the requisite process parameters for good-quality screw extrusion additive manufacturing (AM) of thermoplastic polyolefin (TPO) using fused granulate fabrication (FGF). TPO is a non-hygroscopic, cheaper, and less dense alternative to the well-established thermoplastic polyurethane (TPU). TPO was found to extrude correctly at 170 °C, on a glass build plate at 80 °C with Magigoo PP adhesive. A water uptake test on TPO reported a mass gain plateau of 0.25%, which is significantly lower than that of TPU, which suggests that TPO may not require drying before 3D printing. Tensile testing on FGF TPO specimens achieved similar stress at yield as well as stress and strain at break as indicated by the data sheet for the XY and YZ orientations. The Z direction is significantly weaker than the X and Y orientations, reaching only 30% of the stress at break. TPO achieved the best average stress at yield of 6.36 MPa using the 0.4 mm nozzle with XY printing orientation and stress and strain at break of 13.8 MPa and 1300% at YZ orientation and 1 mm nozzle. The setup achieved relatively high-quality prints of complex geometries, including the popular torture-test Benchy and a child-sized orthotic insole.